Diffraction With A Single Slit And A Lens.

[chris_avfc]

Homework Statement

Trying to find the number of diffraction maxima and the width of the whole pattern.
$\lambda = 500nm$
$b = 2.8μm$ (Slit Width)
$f = 100mm$
$r = 25mm$
$L = 25mm$ (Slit to Lens)

Homework Equations

I have the worked out the irradiance formula as:

$$I(\theta)=I_0 sin^2(\beta)/(\beta^2)$$

The conditions for minima

$$b sin\theta = m\lambda$$

Angular width of central fringe

$$\Delta\theta \approx 2\lambda/b$$

Width of central fringe

$$W \approx 2L\lambda/b$$

The Attempt at a Solution

As said I worked out the irradiance formula, and I think to find the width of the whole pattern you would do:

$(Fringe Width \times 2) + 1$

As then it accounts for the dark fringes as well, plus the one extra for the central.

As for working out the number of maxima, I would guess it would involve the condition for a minimum as it contains the order of diffraction.

What really throws me off though, is the lens, I'm not sure what that would do for the calculations.

 

[chris_avfc]

Sorry to bump this, but does anybody have any idea?

 

[chris_avfc]

Going to be a pain and see if anyone can help me again?

Can't get anywhere with this. :(